1. Field of the Invention
The present invention relates to a method for cleaning a painting apparatus, which cleans paint remained in the painting apparatus, e.g., passages when the paint is changed to another color or to another type for next work, e.g., automobiles.
2. Description of Related Art
FIG. 1 is a schematic view showing a typical painting apparatus. In FIG. 1, reference numeral 1 is a color switching painting apparatus. The color switching painting apparatus 1 comprises a first manifold 2, paint reservoirs 3, 3' each containing paint having a different color, volumetric force feeding pumps 4, 4' for supplying the paint from the paint reservoirs 3, 3' to the manifold 2 through paint supply pipes 5, 5', solenoid valves 6, 6' placed on the paint supply pipes 5, 5', a thinner reservoir 7 containing thinner, a force feeding pump 8 for supplying thinner from the thinner reservoir 7 to the manifold 2 though a thinner supply pipe 9, a solenoid valve 10 placed on the thinner supply pipe 9, a gas supply 11 for supplying air, nitrogen and others, a gas supply pipe 12, a solenoid valve 13 placed on the gas supply pipe 12, a first painting robot 14 connected to the manifold 2 with a hose 15, second and third manifolds 2', 2" to which the same members as the first manifold 2 are connected, a second painting robot 14' connected to the manifold 2' with a hose 15', a third painting robot 14" connected to the manifold 2" with a hose 15", a robot control device 16 to which the first, second and third painting robots 14, 14', 14" are connected with control signal cables 17, and a color switching control device 18 to which the first, second and third manifolds 2, 2', 2" are connected with control signal cables 19. The control signal cables 19 are connected to the solenoid valves 6, 6', 10, 13, the volumetric force feeding pumps 4, 4', the force feeding pump 8 and others through the manifolds 2, 2', 2", which are not shown in detail in FIG. 1.
There is a painting chamber 20 in which a work W is painted in the color switching painting apparatus 1. In the painting chamber 20, the work to be painted W is mounted on a dolly 22 shown in FIG. 2 and transferred to the painting chamber 20 along a transferring line 21. Provided at the head 22a of the dolly 22 is a removable paint color indicating plate 23 having paint color indicating holes 24. There provided a light emitting device 25 and a light receiving device 26 opposed to each other at the entrance of the painting chamber 20 in the transferring line 21.
In order to change the paint color for the next work W, a light emitting unit 25 emits light and when a light receiving unit 26 receives the light coming through the paint color indicating holes 24, it generates a signal. The generated signal is applied to the robot control device 16 and the color switching control device 18, and then the robot control device 16 and the color switching control device 18 start cleaning the paint remained in the painting apparatus for the next work after the painting of the current work is finished.
The paint color indicating plate 23 has one or a plurality of the paint color indicating holes 24 corresponding to the paint colors. For example, forming two color indicating holes 24 shown in FIG. 2 is meant that the paint color is white. One light source for emitting thick beams can be used as the light emitting unit 25, and a plurality of the light receiving unit 26 are arranged corresponding to the plurality of the paint color indicating holes 24. In the case of FIG. 2, two light receiving units 26 receive the light emitting from the light emitting device 25 through the paint color indicating holes 24, so that the paint color can be distinguished as white. Therefore, the paint color indicating holes 24 indicate the paint color by the number of holes 24. Alternatively, the paint color indicating holes 24 can be arranged in one line so as to be binary digits (hole is 1: no hole is 0). In this case, if the used number of the paint color indicating holes 24 is zero to four for the four binary digits, sixteen colors can be distinguished. In the case of the five binary digits, zero to five paint color indicating holes 24 are used and thirty two color can be distinguished.
When the paint color is changed to another color in the painting apparatus, the paint remained in the passages of the painting apparatus has to be cleaned, e.g., with thinner. Conventionally, when the paint color is changed to another color, the same cleaning method is applied for all types of paint, which will be described next.
First, the solenoid valve 13 is opened for four seconds to pass air, nitrogen and others from the air supply 11 through the gas supply pipe 12. Accordingly, the paint remained in the manifold 2, the hose 15 from the manifold 2 to the painting robot 14, the painting robot 14 and others are blown away for four seconds, which is the paint removing gas ejection.
Next, the solenoid valve 10 is opened for three seconds to supply thinner of the thinner reservoir 7 to the manifold 2 through the thinner supply pipe 9 and the force feeding pump 8. Then, the paint remained in the manifold 2, the hose 15 from the manifold 2 to the painting robot 14, the painting robot 14 and others are cleaned by thinner for three seconds, which is the first thinner cleaning.
Thereafter, the solenoid valve 13 is opened for four seconds to supply air from the gas supply 11 to the manifold 2 through the gas supply pipe 12. The thinner remained in the manifold 2, the hose 15 from the manifold 2 to the painting robot 14, the painting robot 14 and others are blown away by gas for four seconds, which is the first thinner removing gas ejection.
Next, similar to the first thinner cleaning, the second thinner cleaning is operated that the paint remained in the manifold 2, the hose 15 from the manifold 2 to the painting robot 14, the painting robot 14 and others are cleaned by thinner for three seconds.
Thereafter, similar to the first thinner removing gas ejection, the second thinner removing gas ejection is operated that the paint remained in the manifold 2, the hose 15 from the manifold 2 to the painting robot 14, the painting robot 14 and others are blown away by gas for 4.5 seconds.
Next, the solenoid valve 6 (or 6') is opened for 4.5 seconds to supply the paint from the paint reservoir 3 (or 3') to the manifold 2 through the volumetric force feeding pumps 4 (or 4') and the paint supply pipe 5 (or 5'). Then, the paint to be used next is filled in the manifold 2, the hose 5 from the manifold 2 to the painting robot 14, the painting robot 14 and others, which is the next-paint filling and which completes the paint color switching.
The total cleaning time in this case is 23 seconds. After the paint color switching is completed, the painting robot 14 is operated by the robot control device 16 to paint the work W.
In the conventional cleaning method, although there are many types of paint, the same cleaning method is applied for all types of paint, which may make the cleaning operation longer and which may increase the manufacturing cost.